When mounting semiconductor chips on a substrate, the substrate is usually made available on a horizontally aligned supporting surface and the semiconductor chips are provided on a wafer table, with the electric connecting surfaces of the semiconductor chips facing upwardly. The semiconductor chip is then removed by a bonding head of an automatic mounting machine, which is a so-called die bonder, and placed on the substrate. This mounting method is known in the field as epoxy die bonding or softsolder die bonding, depending on whether the semiconductor chip is glued with epoxy to the substrate or is soldered with solder to the substrate. The flip chip method differs from this mounting method in that the electric as well as the mechanical connection between the semiconductor chip and the substrate is made via the bumps. To ensure that the semiconductor chip with the bumps can be mounted, it needs to be turned (flipped) by 180° after removal from the wafer table, which explains the name flip chip.
In the flip chip method, the bumps of the semiconductor chip need to be brought into contact with the electric connecting surfaces of the substrate, the so-called pads. The demands placed on placement precision are therefore higher in the flip chip method than in epoxy die bonding. An automatic mounting machine for the mounting of flip chips comprises a flipping apparatus which removes the semiconductor chip from the wafer table and flips the same, a pick-and-place device with a bonding head which receives the flipped semiconductor chip from the flipping apparatus and places the same on the substrate, and three cameras, with the first camera taking a picture of the semiconductor chip presented on the wafer table, the second camera taking a picture of the received semiconductor chip that has already been flipped and is therefore a flip chip, i.e., a picture of the surface of the semiconductor chip provided with the bumps, and a third camera taking a picture of the substrate with the pads. The picture of the first camera is used in order to check the position of the semiconductor chip provided by the wafer table and to newly position the wafer table if necessary, so that the flipping apparatus can receive the semiconductor chip and transfer it to the bonding head. The pictures of the second and third camera are used in order to determine the position of the flip chip and the position of the substrate, so that the bonding head can place the flip chip in a positionally precise manner on the substrate.